Journal articles: 'Equation de Van't Hoff'

1

Holtzer, Alfred. "Persistent confusion on the van't Hoff equation." Biopolymers 42, no. 5 (October 15, 1997): 499–503. http://dx.doi.org/10.1002/(sici)1097-0282(19971015)42:5<499::aid-bip1>3.0.co;2-l.

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2

FAN, Sen, and Yuanhai ZHU. "Application of Van't Hoff Equation to Phase Equilibrium." University Chemistry 33, no. 3 (2018): 70–73. http://dx.doi.org/10.3866/pku.dxhx201711022.

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3

Han, Shu-ying, Hui-min Yu, Yu-qiong Pei, and Yu-mei Chi. "Selectivity-column temperature relationship as a new strategy in predicting separation of structural analogues in HPLC by using different stationary phases." RSC Advances 5, no. 77 (2015): 62686–96. http://dx.doi.org/10.1039/c5ra09524g.

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The effect of changes in column temperature on van't Hoff equation, as well as relationship of separation and column temperature in high performance liquid chromatography (HPLC) by using different stationary phases, have been discussed and compared.

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4

Rao, Sudhakar M., and P. Shivananda. "Role of osmotic suction in swelling of salt-amended clays." Canadian Geotechnical Journal 42, no. 1 (February 1, 2005): 307–15. http://dx.doi.org/10.1139/t04-086.

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The present study examines the influence of extraneous salt addition on pore-fluid osmotic suction of a clay soil. The dependence of swell potentials of the salt-amended clay specimens on initial pore-fluid osmotic suction is also examined. The osmotic suctions predicted by Van't Hoff's equation are in excess or smaller than the values calculated from the pore water electrical conductivity, depending on whether the Van't Hoff factor in the Van't Hoff equation is included or not. Experimental results suggest that the salt-amended specimens absorbed water and swelled in response to matric suction and chemical concentration gradients on inundation with water in oedometer cells. Salt also diffused from the soil pores of salt-amended specimens to the reservoir water in oedometer cells in response to chemical concentration gradients. Reduction in effective stress from osmotic flow into the soil specimen and increase in interparticle repulsion from reduction in pore-water salt concentration rendered the total swell potentials of salt-amended specimens independent of initial pore-fluid osmotic suction. The initial pre-fluid osmotic suction does, however, significantly affect the rate of swelling.Key words: clays, chemical properties, swell potential, suction.

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5

Stepanov, I. A. "The Heats of Chemical Reactions: the Van't-Hoff Equation and Calorimetry." Zeitschrift für Physikalische Chemie 219, no. 8 (August 2005): 1089–97. http://dx.doi.org/10.1524/zpch.2005.219.8.1089.

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6

Son, Changjin, and Sangwoo Lim. "Kinetic Study on the Si₃N₄ Etching in Superheated Water." Solid State Phenomena 314 (February 2021): 113–18. http://dx.doi.org/10.4028/www.scientific.net/ssp.314.113.

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Wet etching of Si3N4 was conducted in superheated water at 160 °C with different additives type and concentration. In general, etching rate of Si3N4 increased with the pH of solution. However, it is difficult to fully explain the Si3N4 etching behavior just with the pH of solution. The OH- concentration (or pH) in superheated water at 160 °C are different from the pH of solution at room temperature. Therefore, the OH- concentrations in superheated water at 160 °C were calculated using van't Hoff equation, equilibrium constant equations, mass and charge balance equations. The calculated OH- concentration at 160 °C showed better correlation with Si3N4 etching rate than that of initial pH of solution.

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7

Xu, Huan Yan, Xue Li, Yan Li, Ping Li, and Wei Chao Liu. "Photocatalytic Degradation of Methyl Orange by TiO₂/Schorl Photocatalyst: Kinetics and Thermodynamics." Applied Mechanics and Materials 713-715 (January 2015): 2789–92. http://dx.doi.org/10.4028/www.scientific.net/amm.713-715.2789.

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An active dye, Methyl Orange (MO) was employed as the target pollutant to evaluate the photocatalytic activity of TiO2/schorl composite and the kinetics and thermodynamics of this process was emphasized in this work. Langmuir–Hinshelwood kinetic model was employed for the kinetic studies and the results revealed that the process of MO photocatalytic discoloration by TiO2/schorl composite followed one order reaction kinetic equation under different conditions. The reaction rate constant (k) increased with initial MO concentration decreasing. When the catalyst dosage or solution pH increased,kvalues increased and then decreased. The possible reasons for these phenomena were discussed. Finally, the thermodynamic parameters ΔG, ΔH, ΔSwere obtained by the classical Van't Hoff equation.

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8

Oberoi, L. M., K. S. Alexander, and A. T. Riga. "Evaluation of an index based on van't Hoff equation to predict PEG-drug eutectic composition." Journal of Thermal Analysis and Calorimetry 78, no. 1 (2004): 83–89. http://dx.doi.org/10.1023/b:jtan.0000042156.21899.de.

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9

Wu, Yun, Hui Mao, Bo Zhao, and Jian Shen. "The interaction of clenbuterol hydrochloride with bovine hemoglobin using spectroscopic techniques and molecular modeling methods." Spectroscopy 23, no. 5-6 (2009): 271–79. http://dx.doi.org/10.1155/2009/696434.

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The interaction of clenbuterol hydrochloride (CL) to bovine hemoglobin (BHb) under physiological conditions was investigated by using UV-vis absorption, fluorescence, circular dichroism (CD) and molecular modeling. The fluorescence intensity of BHb decreased regularly with the gradual increasing concentration of CL. It is observed that there was a prominent interaction between CL and BHb. The fluorescence data revealed that the fluorescence quenching is a static process, and the thermodynamic parameters were calculated according to the Van't Hoff equation. The alternations of protein secondary structure in the presence of CL were determined by the evidence of CD. Molecular modeling study that corroborate our experimental results revealed that the binding mode of CL–BHb complex could be attributed to the hydrophobic interaction and hydrogen bonding, but electronic interaction cannot be excluded.

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10

Gaínza, Alberto Hernández. "Associations of ajmaline and homatropine with bromocresol green and bromophenol blue in dichloromethane: thermodynamic and kinetic parameters." Canadian Journal of Chemistry 65, no. 6 (June 1, 1987): 1279–91. http://dx.doi.org/10.1139/v87-215.

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Ajmaline (AJ) and homatropine (HM) react with bromocresol green (BCG) and bromophenol blue (BPB) in dichloromethane forming 1:1 and 1:2 ion pairs clearly in a chemical equilibrium. Thermodynamic parameters ΔG0, ΔH0, and ΔS0 are calculated using the Van't Hoff equation. In a large excess of HM a product P is formed from the 1:2 ion pair in a pseudo-first order kinetic process which fits Arrhenius' equation. The P product has been identified as a type of charge transfer complex. The thermodynamic parameters corresponding to the formation of the ion pairs BPB—(AJ)2, BCG—(AJ)2, BPB—(HM)2, and BCG—(HM)2 are, respectively: ΔG0 at 294 K, −26, −21, −26, and −19 kJ/mol; ΔH0, −63, −39, −63, and −61 kJ/mol; ΔS0, −125, −62, −125, and −138 J/K mol (ΔH0 and ΔS0 determined in a 288 to 313 K range). The values of the activation energy, Ea, for the reaction of HM (in large excess) with BCG and BPB are 58 and 91 kJ/mol.

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11

Liu, Baosheng, Hongcai Zhang, and Xu Cheng. "Exploring the Interaction of Tartrazine and Lipase: A Multispectroscopic Analysis, Docking and Computational Simulation Methods." Asian Journal of Pharmaceutical Research and Development 7, no. 4 (August 14, 2019): 1–7. http://dx.doi.org/10.22270/ajprd.v7i4.546.

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The interaction between food colorant tartrazine and lipase was studied by multi-spectroscopic and molecular docking simulation under simulated physiological conditions to evaluate the toxic of tartrazine at the protein level. The results showed that tartrazine could effectively quench the endogenous fluorescence of lipase. The thermodynamic parameters were obtained from the van't Hoff equation, and the Gibbs free energy ΔG<0, indicating that the reaction was spontaneous; ΔH<0, ΔS>0, indicating hydrophobic interaction played a major role in forming the tartrazine-lipase complex. as shown by the synchronous fluorescence, UV-vis absorption and circular dichroism data, tartrazine could lead to the conformational and micro environmental changes of lipase, which may affect its physiological function. Molecular docking results showed that tartrazine was site in the active center of lipase, which altered the microenvironment of amino acid residues at the catalytic active center of lipase.

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12

Lone Jr., Irfan H. "Interpretation and Significance of the Alternative Formulation of Van’t Hoff Equation." Academic Journal of Chemistry, no. 41 (January 15, 2018): 01–03. http://dx.doi.org/10.32861/jac.41.01.03.

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The interpretation and significance of the alternative form of Van’t Hoff equation in the context of effect of temperature on the equilibria of exothermic and endothermic processes has been discussed. The central role that entropy plays in determining the dependence of equilibrium constant on temperature has been emphasized.

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13

Prickett, Richelle C., Janet A. W. Elliott, Shamina Hakda, and Locksley E. McGann. "A non-ideal replacement for the Boyle van’t Hoff equation." Cryobiology 57, no. 2 (October 2008): 130–36. http://dx.doi.org/10.1016/j.cryobiol.2008.07.002.

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14

Chugunov, Alexander S., Vadim A. Vinnitskii, and Pavel N. Zuev. "THE ROLE OF SORPTION PROCESSES IN THE TRANSMEMBRANE TRANSFER OF ALKALINE METAL SALTS THROUGH A NANOFILTRATION MEMBRANE." Bulletin of the Saint Petersburg State Institute of Technology (Technical University) 56 (2021): 3–11. http://dx.doi.org/10.36807/1998-9849-2020-56-82-3-11.

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The article provides data on the effect of the concentration of I-I electrolyte salt on the transfer through the Vontron VNF 1812 nanofiltration membrane. Data for NaNO3, NaCl, NaHCO3, NaH2PO4 and alkali metal nitrates are presented. The experimental data obtained suggest that the flux of water and salt are determined by the interaction of anions with protonated amino groups, which are part of the material of the selective membrane layer. An increase in the transmembrane flux of alkali metal nitrates is observed in the series CsNO3>KNO3>NaNO3>LiNO3. This series is opposite to the series of selectivity in the sorption of metals on carboxyl cation exchangers, but this series coincides with the series of increasing diffusant mass. It is noted that for all the solutions under study, water transfer can occur at an operating pressure significantly lower than the osmotic pressure calculated by the Van't Hoff equation, which indicates the essential role of filtration in the traditional understanding of this term

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15

Demirhan, Hulya, Mustafa Arslan, Mustafa Zengin, and Mustafa Kucukislamoglu. "Investigation of Charge Transfer Complexes Formed between Mirtazapine and Someπ-Acceptors." Journal of Spectroscopy 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/875953.

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Charge transfer complexes (CTC) of mirtazapine with tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), and tetracyanoquinodimethane (TCNQ) have been studied spectrophotometrically in dichloromethane at room temperature. The stoichiometries of the complexes were found to be 1 : 1 ratio by the Job Method between mirtazapine and the acceptors. The equilibrium constants and thermodynamic parameters of the complexes were determined by the Benesi-Hildebrand and Van't Hoff equations. Mirtazapine in pure and dosage form was applied in this study. The results indicate that the formation constants for the complexes depend on the nature of electron acceptors and donor. And also the spectral studies of the complexes were determined by FT-IR and NMR spectroscopy.

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16

Kutsuna, Shuzo. "Experimental determination of Henry's law constants of difluoromethane (HFC-32) and the salting-out effects in aqueous salt solutions relevant to seawater." Atmospheric Chemistry and Physics 17, no. 12 (June 21, 2017): 7495–507. http://dx.doi.org/10.5194/acp-17-7495-2017.

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Abstract. Gas-to-water equilibrium coefficients, KeqS (in M atm−1), of difluoromethane (CH2F2), a hydrofluorocarbon refrigerant (HFC-32), in aqueous salt solutions relevant to seawater were determined over a temperature (T) range from 276 to 313 K and a salinity (S) range up to 51 ‰ by means of an inert-gas stripping method. From the van't Hoff equation, the KeqS value in water, which corresponds to the Henry's law constant (KH), at 298 K was determined to be 0.065 M atm−1. The salinity dependence of KeqS (the salting-out effect), ln(KH∕KeqS), did not obey the Sechenov equation but was proportional to S0. 5. Overall, the KeqS(T) value was expressed by ln(KeqS(T)) = −49.71 + (77.70 − 0.134 × S0. 5) × (100∕T) + 19.14 × ln(T∕100). By using this equation in a lower-tropospheric semi-hemisphere (30–90 °S) of the Advanced Global Atmospheric Gases Experiment (AGAGE) 12-box model, we estimated that 1 to 4 % of the atmospheric burden of CH2F2 resided in the ocean mixed layer and that this percentage was at least 4 % in the winter; dissolution of CH2F2 in the ocean may partially influence estimates of CH2F2 emissions from long-term observational data of atmospheric CH2F2 concentrations.

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17

Fathi-Azarbayjani, Anahita, Masoumeh Abbasi, Jalil Vaez-Gharamaleki, and Abolghasem Jouyban. "Measurement and correlation of deferiprone solubility: Investigation of solubility parameter and application of van't Hoff equation and Jouyban–Acree model." Journal of Molecular Liquids 215 (March 2016): 339–44. http://dx.doi.org/10.1016/j.molliq.2015.12.005.

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18

Kiss, G., and H. C. Hansson. "Application of osmolality for the determination of water activity and the modelling of cloud formation." Atmospheric Chemistry and Physics Discussions 4, no. 6 (November 24, 2004): 7667–89. http://dx.doi.org/10.5194/acpd-4-7667-2004.

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Abstract. A simple approach is suggested here to give reliable estimates on the Raoult term of the Köhler equation when calculating critical supersaturation (Sc) for real atmospheric samples. Water activity is calculated from osmolality and thus the original Köhler equation can be applied avoiding the difficulties with unknown molecular weights, solubilities, van't Hoff factors of aerosol constituents and also the interactions in the growing droplet. First, water activity calculated from osmolality data was compared to literature values both for electrolytes and a non-electrolyte. Then the applicability of the approach was demonstrated by generating Köhler curves from osmolality derived and literature activity data as well as by using the simplified Köhler equation. Sc values calculated with the osmolality approach fitted those obtained by using literature water activity data within a relative deviation of less than 0.3%, 0.8%, 1.1% and 3.4% for sucrose, CaCl2, NaCl and H2SO4, respectively, while the corresponding errors with the simplified Köhler equation were 11%, 8.5%, 4.5% and 19% in the dry nucleus size range of 20 nm to 100 nm. Finally, the osmolality method was used to show how considerably Sc is underestimated for organic acids if complete dissociation is assumed. The method described in this paper can be applied to real atmospheric samples (aerosol extracts, fog water or cloud water) thus improving the reliability of estimates on critical supersaturation and critical droplet diameter in atmospheric modelling.

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19

Deiters, Ulrich K. "The isothermal van’t Hoff equation for phase equilibria—A forgotten relation?" Fluid Phase Equilibria 336 (December 2012): 22–27. http://dx.doi.org/10.1016/j.fluid.2012.08.028.

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20

Lima, Eder C., Adriano A. Gomes, and Hai Nguyen Tran. "Comparison of the nonlinear and linear forms of the van't Hoff equation for calculation of adsorption thermodynamic parameters (∆S° and ∆H°)." Journal of Molecular Liquids 311 (August 2020): 113315. http://dx.doi.org/10.1016/j.molliq.2020.113315.

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21

Chen, Wen-Yih, Hsiang-Ming Huang, Chien-Chen Lin, Fu-Yung Lin, and Yu-Chia Chan. "Effect of Temperature on Hydrophobic Interaction between Proteins and Hydrophobic Adsorbents: Studies by Isothermal Titration Calorimetry and the van't Hoff Equation." Langmuir 19, no. 22 (October 2003): 9395–403. http://dx.doi.org/10.1021/la034783o.

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22

Shiau, Lie-Ding. "A Linear Regression Model for Determining the Pre-Exponential Factor and Interfacial Energy Based on the Metastable Zone Width Data." Crystals 10, no. 2 (February 11, 2020): 103. http://dx.doi.org/10.3390/cryst10020103.

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A linear regression model is presented in this study to determine the pre-exponential factor and interfacial energy of the crystallized substance based on classical nucleation theory using the metastable zone width data. The nucleation event is assumed corresponding to a point at which the total number density of the nuclei has reached a fixed (but unknown) value. One equation is derived for any temperature-dependent functional form of the solubility. Another equation is derived for the van’t Hoff solubility expression. The pre-exponential factor and interfacial energy obtained from these two equations are found consistent for the studied systems, including glutamic acid, glycine, and 3-nito-1,2,4-triazol-5-one. The results obtained from these two equations are also compared with those obtained from the integral method and classical 3D nucleation theory approach.

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23

Petrunkina, A. M., and E. Töpfer-Petersen. "Heterogeneous osmotic behaviour in boar sperm populations and its relevance for detection of changes in plasma membrane." Reproduction, Fertility and Development 12, no. 6 (2000): 297. http://dx.doi.org/10.1071/rd00087.

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The spermatozoa of most mammals behave as ‘perfect osmometers’. The volume response to osmolality obeys the Boyle–Van’t Hoff relationship (i.e. volume changes are determined by the osmotically active fraction of the cell volume (solids and water)). Most evaluations of osmotic sperm cell behaviour have been based on the mean volume of the cell population. In the present study, both mean and modal volumes of samples of sperm were evaluated. Both mean and modal volumes responded to environmental osmolality via the Boyle–Van’t Hoff relationship; however, the modal volume showed a more sensitive response than the mean volume. This was confirmed for both ejaculated and epididymal spermatozoa. After incubation under capacitating conditions, the difference in modal and mean volume response of ejaculated sperm was considerably diminished and, in epididymal sperm, completely abolished. The sperm osmotic behaviour was still consistent with the Boyle–Van’t Hoff equation, but the apparent osmotically inactive modal cell volume decreased after exposure to capacitating conditions in both ejaculated and epididymal sperm samples. The changes in epididymal sperm were more intensive. Due to its enhanced sensitivity to environmental osmolality and incubation under capacitating conditions, the modal volume could be used as a parameter for evaluating sperm population response, such as for detecting environmentally or cryopreservation-induced membrane changes.

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24

Sedlbauer, Josef. "Modeling Approaches to Hydration Properties of Aqueous Nonelectrolytes at Elevated Temperatures and Pressures." Collection of Czechoslovak Chemical Communications 73, no. 3 (2008): 322–43. http://dx.doi.org/10.1135/cccc20080322.

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Thermodynamic models describing temperature and pressure evolution of Henry's law constant and related properties of hydration of aqueous nonelectrolyte solutes are reviewed. The included models cover a broad range spanning from simple van't Hoff-like equations used in environmental chemistry over the more elaborate empirical or semiempirical temperature correlations favored for engineering purposes to complete equations-of-state for hydration properties originating in the theory of near-critical phenomena and developed for modeling of hydrothermal systems. For aqueous organic solutes, the methods are often coupled with the group additivity approximation, leading to complex tools for predicting the properties of solutions containing organic species. The various models were subjected to tests documenting their expected range of applicability at elevated pressures (for acid gases) or at high temperatures (for hydrocarbons and oxygen-containing organic solutes). New developments in the field are discussed and some future needs are envisioned.

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25

Bordbar, Abdol-Khalegh, Sayed Habib-Allah Mousavi, and Hamid Dazhampanah. "Analysis of oxygen binding by hemoglobin on the basis of mean intrinsic thermodynamic quantities." Acta Biochimica Polonica 53, no. 3 (October 1, 2006): 563–68. http://dx.doi.org/10.18388/abp.2006_3328.

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The binding data for oxygenation of human hemoglobin, Hb, at various temperatures and in the absence and presence of 2,3-diphosphoglycerate, DPG, and inositol hexakis phosphate, IHP, were analyzed for extraction of mean intrinsic Gibbs free energy, DeltaGo, enthalpy, DeltaHo, and entropy, DeltaSo, of binding at various partial oxygen pressures. This method of analysis considers all the protein species present such as dimer and tetramer forms which were not considered by Imai et al. (Imai K et al., 1970, Biochim Biophys Acta 200: 189-196), in their analysis which was based on Adair equation. In this regard, the values of Hill equation parameters were estimated with high precision at all points of the binding curve and used for calculation of DeltaGo, DeltaHo and DeltaSo were also calculated by analysis of DeltaGo values at various temperatures using van't Hoff equation. The results represent the enthalpic nature of the cooperativity in Hb oxygenation and the compensation effect of intrinsic entropy. The interpretation of results also to be, into account the decrease of the binding affinity of sites for oxygen in the presence of DPG and IHP without any considerable changes in the site-site interaction (extent of cooperativity). In other words, the interactions between bound ligands, organic phosphates and oxygen, are more due to a decreasing binding affinity and not to the reduction of the cooperative interaction between sites. The results also document the more heterotropic effect of IHP compared to DPG.

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26

Yanovskiy, L. S., V. M. Ezhov, M. A. Ilina, and K. V. Sharanina. "Stady of the thermal-oxidative stability of synthetic oils for aircraft gas turbine engines and helicopter gearboxes." World of Oil products the Oil Companies Bulletin 02 (2021): 52–56. http://dx.doi.org/10.32758/2071-5951-2021-0-2-52-56.

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The aim of the research was to develop a method for determining the values of aviation oils during their oxidation based on the theories of chemical kinetics. Studies of the thermal-oxidative stability (TOS) of aviation lubricating oils based on polyesters for gas turbine engine aircraft were carried out using the method based on GOST 23797-79. The values of the kinematic viscosity at temperatures of 100 °C and minus 40 °C, as well as the acid number of samples of oils LZ-240, ASMO-200M, ASMO-220 and VASMO-225M, oxidized for 10, 20, 30, 40 and 50 hours at temperatures of 200, 225 and 240 °C were determined. Based on the results obtained, kinetic graph changes in oil parameters are constructed, the reaction order is determined, and models of changes in oil parameters during oxidation based on the Arrhenius equation and the Van't-Hoff rule are proposed. The calculation error does not exceed 10%. Dependencies of oxidation temperature and oxidation time are built, where maximum permissible values of oil parameters are achieved. These function allow you to evaluate the operability of oils and the quality margin according to its TOS.

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Chen, Zi Dan, Kun Kun Wang, Xue Li, Sheng Wang, Sha Wu, Min Li, and Er Hong Duan. "Solubility and Thermodynamic Properties of L-Proline in Methanol-Dichloromethane Mixtures." Applied Mechanics and Materials 775 (July 2015): 185–90. http://dx.doi.org/10.4028/www.scientific.net/amm.775.185.

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The solubility of L-proline in binary solvents of methanol and dichloromethane were measured by a dynamic method via a laser monitoring technique. In the binary solvent mixtures, the solubility increases with the increasing of temperature and proportion of the methanol. The experimental solubility were fitted to modified Apelblat equation and Van’t Hoff equation in this work can be used as essential data and models in the purification process of L-proline. The dissolving process is endothermic and the dissolution driving force converts from enthalpy-driving to entropy-driving.

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Bhalu, Ankita A., Kapil D. Bhesaniya, Nayan J. Vekariya, and Shipra H. Baluja. "Chalcones: A Solubility Study at Different Temperatures." International Letters of Chemistry, Physics and Astronomy 31 (March 2014): 7–19. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.31.7.

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Some new chalcones are synthesized by the condensation of aryl ketones with aromatic aldehydes and solubility of these synthesized chalcones is determined in chloroform and dichloromethane at temperatures ranging between 293.15 K and 313.15 K by gravimetric method. The experimental data was correlated well with modified Apelblat equation. Further, from the experimental solubility data, some thermodynamic parameters such as dissolution enthalpy, Gibb’s energy and entropy etc. were evaluated using van’t Hoff equation. The positive Gibb’s energy and negative entropy suggests spontaneous dissolution and more ordered structure in solution.

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Corrêa, Paulo Cesar, Maycon Fagundes Teixeira Reis, Gabriel Henrique Horta de Oliveira, Ana Paula Lelis Rodrigues de Oliveira, and Fernando Mendes Botelho. "Moisture desorption isotherms of cucumber seeds: modeling and thermodynamic properties." Journal of Seed Science 37, no. 3 (September 2015): 218–25. http://dx.doi.org/10.1590/2317-1545v37n3149549.

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Hygroscopic equilibrium curves or sorption isotherms are important in order to define dehydration limits of the product, estimate moisture content alterations under environment conditions and to acquire moisture content values for safe storage. This work aimed to determine desorption isotherms of cucumber seeds stored at different temperature (10, 20, 30, 40 and 50 ºC) and relative humidity (0.11 to 0.96) and the thermodynamic properties of this process. Mathematical models were fitted to experimental data in order to represent the agricultural products hygroscopicity. Net isosteric heat of desorption was performed based on the Clausius-Clapeyron thermodynamic relation and Gibbs free energy through the Van't Hoff equation. Based on statistical parameters, Modified Henderson model was the one that best represented hygroscopicity of cucumber seeds. Equilibrium moisture content of cucumber seeds decreased with temperature increment at a constant value of relative humidity. Differential enthalpy values, representing the energy required to remove moisture from the cucumber seeds, ranged from 2923 to 2469 kJ. kg-1. Values of differential entropy and Gibbs free energy decreased with moisture content increase. Enthalpy-entropy compensation theory is valid for the sorption of cucumber seeds, in which the water sorption mechanism in cucumber seeds can be considered to be enthalpy controlled.

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Saha, Tapan K., Subarna Karmaker, and Md F. Alam. "Kinetics, mechanism and thermodynamics involved in sorption of meso-tetrakis(4-sulfonatophenyl)porphyrin onto chitosan in aqueous medium." Journal of Porphyrins and Phthalocyanines 18, no. 03 (March 2014): 240–50. http://dx.doi.org/10.1142/s1088424613501174.

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Sorption of meso-tetrakis(4-sulfonatophenyl)porphyrin ( H 2 tpps ) onto chitosan has been investigated in aqueous medium. Kinetic and isotherm studies were carried out by considering the effects of various parameters, such as pH, initial concentration of H 2 tpps solution, and temperature. The kinetic data obtained from different batch experiments were analyzed using pseudo first-, second-order, intraparticle, and film diffusion kinetic models. The equilibrium sorption data was analyzed by using Tempkin, Langmuir and Freundlich models. The best results were achieved with the pseudo second-order kinetic, Langmuir and Freundlich isotherm models. The intraparticle diffusion and film diffusion are the rate limiting steps. The amount of sorbate adsorbed at equilibrium (qe) increased with increasing the initial concentration of H 2 tpps solution, showing maximum sorption capacity of 445.21 μmol.g-1. The activation energy (Ea) of sorption kinetics was found to be 19.47 kJ.mol-1. Thermodynamic parameters such as change in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were evaluated by applying the Van't Hoff equation. Thermodynamic activation parameters such as change in enthalpy of activation (ΔH‡), entropy of activation (ΔS‡), and free energy of activation (ΔG‡) were also calculated. The thermodynamics of H 2 tpps sorption onto chitosan in aqueous medium indicates its spontaneous and endothermic nature.

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Ge, Qiang, Xu Jia Ding, Gang Wu, Song Liang, and Si Zhu Wu. "Study on the Microstructure and Mechanical Properties of PET and PET/PTT Blends." Key Engineering Materials 340-341 (June 2007): 1085–90. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.1085.

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In this study, the thermal analysis FTIR Micro-Spectroscopy method was used to observe the energy changes of the functional groups of Poly(ethylene terephthalate) (PET) during manufacturing progress. The conformational apparent enthalpy H in the melting process has been calculated by the van’t Hoff equation at the constant pressure and then plotted with temperature. The structure and properties of PET/PTT (Polytrimethylene Terephthalate) blends with different blending ratio had also been studied by using DSC and DMA analysis.

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Myszograj, Sylwia. "Reaction rate coefficient k20 and temperature coefficient Θ in organic waste thermal disintegration." ITM Web of Conferences 23 (2018): 00026. http://dx.doi.org/10.1051/itmconf/20182300026.

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It was described the test of sewage sludge and organic fraction of municipal mixed solid waste thermal disintegration process. The waste activated sludge used during the tests was collected from the secondary settlement tank in a mechanical-biological wastewater treatment plant. The biowaste used in the studies was collected from an area of new buildings. It was noticed from means values of Soluble Chemical Oxygen Demand (SCOD) plot that both heating temperature and time, influence the amount of dissolved COD. The observations indicate that changes of SCOD can be described by an increasing, differentiable function of time and the rate of change of the soluble COD in the hydrolysates, in time is proportional to the difference of the maximum values of SCOD and its value in time, which leads to the relationship of the first-order ordinary differential equation. The process effectiveness depending on the temperature was described with the mathematical model including Van't Hoff-Arrhenius equation. Inspection of the data and some preliminary fits indicates, that for the description of changes in SCOD terms of time and temperature were adopted the form of nonlinear mixed model. Values of k20 indicator and Θ parameter depend on the substrate type. For waste activated sludge thermal disintegration, value of reaction speed indicator k20 was 0.028 h-1 (0,67 d-1), and value of temperature indicator equalled Θ = 1.024. For thermal disintegration of biological waste, value of reaction speed indicator k20 was 0.016 h-1 (0,38 d-1), and value of temperature indicator equalled Θ = 1.016.

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33

Al-Omari, Saleh. "Separation of static and dynamic thermodynamic parameters for the interaction between pyropheophorbide methyl ester and copper." Journal of Porphyrins and Phthalocyanines 18, no. 04 (April 2014): 297–304. http://dx.doi.org/10.1142/s1088424614500023.

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The interaction between pyropheophorbide methyl ester (PPME) and the ionic metal of copper ( Cu 2+) was investigated using fluorescence and UV-vis techniques. By analysis of the fluorescence spectra, it was observed that Cu 2+ has a strong ability to quench the intrinsic fluorescence of PPME through dynamic and static quenching process. The binding constants of Cu 2+ with PPME were determined at different temperatures depending on the results of fluorescence quenching. Based on the modified form of the Stern–Volmer equation, static binding constant (kS) and the dynamic binding constant (kD) of Cu 2+-PPME association were obtained at different temperatures. The static thermodynamic function of the enthalpy change (ΔHS), the dynamic thermodynamic function of the enthalpy change (ΔHD), the static thermodynamic function of the entropy change (ΔSS), and the dynamic thermodynamic function of the entropy change (ΔSD) for the binding interaction were determined according to the van't Hoff equation. The values of static Gibbs free energy change (ΔGS) and dynamic Gibbs free energy change (ΔGD) were determined to be negative indicating that the interaction process was a spontaneous. ΔHD and ΔSD values were positive indicating that the dynamic quenching process of Cu 2+-PPME interaction was driven mainly by hydrophobic forces. For the static binding quenching, ΔHS and ΔSS values were negative which indicated that hydrogen bond, electrostatic interaction, and van der Waals interaction were important driving forces for PPME- Cu 2+ association. Both static and dynamic fluorescence quenching were related to the distance between PPME and Cu 2+ indicating that the electron transfer process occurred.

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Arai, Koichi, and John D. Ferry. "Temperature Dependence of Viscoelastic Properties of Carbon-Black-Filled Rubbers in Small Shearing Deformations." Rubber Chemistry and Technology 59, no. 4 (September 1, 1986): 592–604. http://dx.doi.org/10.5254/1.3538221.

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Abstract Measurements of dynamic storage and loss shear moduli G′ and G″ (0.12 to 2 Hz) and shear relaxation modulus G(t) (up to 104 s) have been made on six vulcanized and one unvulcanized carbon-black-filled rubber compounds over a temperature range from −22.5° to 63°C. The maximum shear strain in the oscillatory deformations was less than 0.005 and in the stress relaxation measurements, 0.015. The temperature dependence of viscoelastic properties could not be fully described in terms of horizontal shifts (αT) of logarithmic time or frequency scales. It could, however, be largely described by vertical shifts (ST) corresponding to uniform temperature dependence of the magnitudes of contributions to modulus from a spectrum of relaxation mechanisms. There were some departures from this behavior, especially in a blend containing two rubber species and in the unvulcanized compound at long times. The temperature dependence of the ST shift factors followed the van't Hoff equation with values of ΔH from 5.9 to 14.7 kJ/mole, attributable to a heat of dissociation of contacts between particle aggregates. The slow relaxation over many logarithmic decades of time scale in the rubbery zone of viscoelastic behavior is attributed to adjustments of such contacts by Brownian motion, which leave the density of the structure unchanged as shown by constancy of the differential dynamic modulus measured by superposed small oscillating deformations.

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35

Williams, Celia K., William C. Galley, and G. Ronald Brown. "The influence of competing factors on the endothermic nature of bile salt binding by cationic adsorbent." Canadian Journal of Chemistry 81, no. 2 (February 1, 2003): 133–40. http://dx.doi.org/10.1139/v03-003.

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The binding of sodium chenodeoxycholate, a hydrophobic bile salt, by a polyacrylamide resin with N,N,N-trimethylammonium dodecyl chloride (QPDA12) pendant groups was studied in the presence of elevated concentrations of competing anions. The equilibrium bile salt concentration was determined from HPLC data for a range of initial bile salt concentrations. Binding constants extracted from the fit of the isotherms to the Langmuir equation were obtained for data for temperatures from 24 to 60°C. A reduction in chenodeoxycholate binding affinity was observed in comparison with that reported previously at lower overall anion concentrations. A van't Hoff analysis of the data revealed that a decrease in the favourable entropy of binding was responsible for this reduced affinity. Decomposition of the binding constants into specific contributions for the competing buffer anions and the chenodeoxycholate anion returned positive values of ΔH° and ΔS° for the binding of both the competing ions and bile salt. These findings reveal that the weakening of the bile salt binding that occurs with added salt is not due to Debye screening of an attraction between ions of opposite charge. A binding mechanism consistent with the thermodynamics observed was proposed in which the dominant role of hydration changes that occur on binding provides the principal driving force for the process.Key words: bile salts, endothermic binding, polymer sorbents, solvent randomization.

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36

Narsilio, Guillermo A., David W. Smith, and Peter Pivonka. "Estimating vertical and lateral pressures in periodically structured montmorillonite clay particles." Anais da Academia Brasileira de Ciências 82, no. 1 (March 2010): 13–24. http://dx.doi.org/10.1590/s0001-37652010000100003.

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Given a montmorillonitic clay soil at high porosity and saturated by monovalent counterions, we investigate the particle level responses of the clay to different external loadings. As analytical solutions are not possible for complex arrangements of particles, we employ computational micromechanical models (based on the solution of the Poisson-Nernst-Planck equations) using the finite element method, to estimate counterion and electrical potential distributions for particles at various angles and distances from one another. We then calculate the disjoining pressures using the Van't Hoff relation and Maxwell stress tensor. As the distance between the clay particles decreases and double-layers overlap, the concentration of counterions in the micropores among clay particles increases. This increase lowers the chemical potential of the pore fluid and creates a chemical potential gradient in the solvent that generates the socalled 'disjoining' or 'osmotic' pressure. Because of this disjoining pressure, particles do not need to contact one another in order to carry an 'effective stress'. This work may lead towards theoretical predictions of the macroscopic load deformation response of montmorillonitic soils based on micromechanical modelling of particles.

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Song, Jing Yan, and Ling Rong He. "Thermodynamics of Organic Dyes Adsorption onto Thermal Modified Rectorite." Advanced Materials Research 463-464 (February 2012): 194–97. http://dx.doi.org/10.4028/www.scientific.net/amr.463-464.194.

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Adsorption behavior of Rhodamine B (RhB) onto thermal modified rectorite (TM-R) has been thermodynamically investigated. The thermal modified rectorite prepared at different temperatures was characterized by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET). The analysis of the isotherm equilibrium data using the Langmuir and Freundlich equations by linear methods showed that the data fitted better with Freundlich model than the Langmuir model. Thermodynamic parameters were calculated based on Van’t Hoff equation. The average change of standard adsorption heat of RhB was 88.96 kJ/mol. The adsorption Gibbs free energy changes are in the range of -26.88～-34.52 kJ/mol, The negative of adsorption Gibbs free energy changes in all cases are indicative of the spontaneous nature of the adsorption interaction, and the values of adsorption entropy changes are positive.

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38

Xie, Jiao, Kanghuai Zhang, Haitao Wang, Xin Yang, Wenbin Mao, Chenwei Liu, and Na Wang. "Determination of the Solubility, Dissolution Enthalpy, and Entropy of Icariin in Acetone, Acetoacetate, Chloroform, and Light Petroleum." Natural Product Communications 15, no. 11 (November 2020): 1934578X2097149. http://dx.doi.org/10.1177/1934578x20971491.

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The solubility of icariin in acetone, acetoacetate, chloroform, and light petroleum in the 283.2‐318.2 K range was measured by ultraviolet-visible spectrophotometry. As the temperature increased, the solubility of icariin in the 4 solvents gradually increased. The solubility data correlated with the modified Apelblat equation. The dissolution enthalpy and entropy of icariin were determined using van’t Hoff plots. The dissolution enthalpy and entropy of icariin in the 4 solvents increases as acetone >acetoacetate >chloroform >light petroleum, which can be explained by the difference of the polarity indices between them. The polarity indices of the solvents affect the solubility behavior.

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39

Dezhampanah, Hamid, Abdol-Khalegh Bordbar, and Shahram Tangestaninejad. "Thermodynamic investigation of manganese(III) 5-(1-(4-carboxybutyl)pyridinium-4-yl) 10,15,20-tris-(1-methylpyridinium-4-yl)porphyrin with calf thymus DNA." Journal of Porphyrins and Phthalocyanines 13, no. 08n09 (August 2009): 964–72. http://dx.doi.org/10.1142/s1088424609001224.

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Binding properties of two water-soluble porphyrins, manganese(III) 5-(1-(4-carboxybutyl)pyridinium-4-yl) 10,15,20-tris(1-methylpyridinium-4-yl)porphyrin ( Mn(III)5-CBPyP ) and manganese(III) 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin ( Mn(III)TMPyP ), in the presence of various concentration of calf thymus DNA (ct-DNA), has been studied in 7.5 mM phosphate buffer, pH = 7.2 and at various temperatures by UV-vis absorption, resonance light scattering (RLS) and fluorescence spectroscopy and viscosity measurement. Optical absorption and RLS measurements have demonstrated three different species of both porphyrins form in DNA solution. The thermodynamic parameters were calculated by van't Hoff equation at various temperatures. The values of -4.89 kJ.mol-1 and +65.98 J.mol-1.K-1 for Mn(III)5-CBPyP and -14.92 kJ.mol-1 and +15.46 J mol-1.K-1 for TMPyP were estimated for enthalpy and entropy changes of interaction, respectively. The data indicate that the process is exothermic and enthalpy- and entropy-driven, suggesting that electrostatic forces play a considerable role in the interaction process. The binding of both porphyins to DNA quenches fluorescence emission of ethidium bromide (EB) and the quenching process obeys linear Stern-Volmer relationship, indicating the quenching of electron transfer of EB from its binding sites by these porphyrins. The results of using these techniques indicate the external mode of binding for both porphyrins and a higher binding affinity of Mn(III)5-CBPyP with respect to Mn(III)TMPyP .

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40

Zhou, Shi Xue, Qian Qian Zhang, Nai Fei Wang, Zong Ying Han, Wei Xian Ran, Chang Zhen Li, Chao Ding, and Peng Bo Li. "Crystallitic Structure and Thermodynamics of Magnesium-Based Hydrogen Storage Materials from Reactive Milling under Hydrogen Atmosphere." Advanced Materials Research 724-725 (August 2013): 1021–24. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.1021.

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Magnesium-based hydrogen storage materials were prepared by reactive milling of magnesium under hydrogen atmosphere with crystallitic carbon, prepared from anthracite coal, as milling aid. The XRD analysis shows that in the presence of 30 wt.% of crystallitic carbon, the Mg easily hydrided into β-MgH2of crystal grain size 29.7 nm and a small amount of γ-MgH2after 3 h of milling under 1 MPa H2. The enthalpy and entropy changes of the hydrogen desorption reaction are 42.7 kJ/mol and 80.7 J/mol K, respectively, calculated by the vant Hoff equation from thep-C-Tdata in 300-380°C.

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41

Rahaman, Habibur, Niloy Roy, Aditi Roy, Samapika Ray, and Mahendra Nath Roy. "Exploring Existence of Host-Guest Inclusion Complex of β-Cyclodextrin of a Biologically Active Compound with the Manifestation of Diverse Interactions." Emerging Science Journal 2, no. 5 (November 4, 2018): 251. http://dx.doi.org/10.28991/esj-2018-01149.

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The host–guest interaction of p-nitro benzaldehyde as guest β-Cyclodextrins have been investigated which have significant applications in the field of medicine such as controlled drug delivery. The 1H NMR study confirms the formation of inclusion complex while surface tension and conductivity studies support the formation inclusion complex with 1:1 stoichiometry. The stoichiometry of the inclusion complex was also supported with Job’s plot method by UV-Visible spectroscopy. FT-IR spectra and SEM study also support the inclusion process. Association constants of the inclusion complexes have been calculated using the Benesi–Hildebrand method, while the thermodynamic parameters have been estimated with the help of van’t Hoff equation.

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42

Dezhampanah, Hamid, and Soghra Fyzolahjani. "Study on Interaction of Cationic Porphyrazine with Synthetic Polynucleotides." Analytical Cellular Pathology 36, no. 5-6 (2013): 125–32. http://dx.doi.org/10.1155/2013/305356.

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Interactions of cationic tetrakis (N, N′, N″, N‴- tetramethyltetra-3, 4-pyridinoporphyrazinatozinc (II) (Zn (tmtppa)) with synthetic polynucleotides, poly (G-C) and poly (A-T), and calf thymus DNA have been characterized in 7.5 mM phosphate buffer of pH 7.2 by UV-Vis absorption and fluorescence spectroscopy. The appearance of hypochromicity more than 30% in UV-Vis spectra of porphyrazine due to interaction of both poly (G-C) and poly (A-T) indicates interaction similar to that of porphyrazine with DNA.The binding constants were determined from the changes in the Q-band maximum of the porphyrazine spectra at various poly (G-C) and DNA concentrations. The values of K were 2.5 × 106M−1, 2.5 × 106M−1and 2.5 × 105M−1for poly (G-C), poly (A-T) and DNA, respectively, at 25°C. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were calculated using the van't Hoff equation at various temperatures. The enthalpy and entropy changes were determined to be 41.14 kJ mol−1and 260.50 J mol−1·K−1for poly (G-C) and 53.59 kJ mol−1and 285.46 J mol−1·K−1for DNA at 25°C. The positive and large values of the entropy and enthalpy suggest that both hydrophobic and electrostatic interactions may play an important role in the stabilization of the complex formation. The binding of polynucleotides to porphyrazine quenches fluorescence emission of ethidium bromide (EB), and the quenching process obeys linear Stern-Volmer relationship. The results reviled groove-binding mode of porphyrazine for both AT- and GC-rich polynucleotides of DNA.

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43

Ahdno, Hossein, and Hoda Jafarizadeh-Malmiri. "Clarification of Date Syrup by Activated Carbon: Investigation on Kinetics, Equilibrium Isotherm, and Thermodynamics of Interactions." International Journal of Food Engineering 11, no. 5 (October 1, 2015): 651–58. http://dx.doi.org/10.1515/ijfe-2015-0093.

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Abstract The present work studies the removal of colored components from date syrup by activated carbon powder. The clarification process was carried out at an experimental batch set up and the role of activated carbon content, temperature and residence time was investigated on adsorption efficiency. The experimental data were analyzed by intra-particle diffusion, pseudo first- and second-order models. The adsorption capacity of activated carbon increases with increase of process temperature. Adsorption kinetics could be best modeled by the pseudo second-order model. Also, Langmuir isotherm describes the equilibrium data variation better than Freundlich and Temkin equations. The feasibility of adsorption was evaluated by measuring color removal at three temperatures and Van’t Hoff equation was used for computation of Gibbs energy. Thermodynamically, the process is endothermic accompanied with increase in randomness and decrease in Gibbs energy. Finally, the optimum temperature for clarification of date syrup was determined to be 50°C.

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44

Shao, Huaiyu, Gongbiao Xin, Xingguo Li, and Etsuo Akiba. "Thermodynamic Property Study of Nanostructured Mg-H, Mg-Ni-H, and Mg-Cu-H Systems by High Pressure DSC Method." Journal of Nanomaterials 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/281841.

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Mg, Ni, and Cu nanoparticles were synthesized by hydrogen plasma metal reaction method. Preparation of Mg2Ni and Mg2Cu alloys from these Mg, Ni, and Cu nanoparticles has been successfully achieved in convenient conditions. High pressure differential scanning calorimetry (DSC) technique in hydrogen atmosphere was applied to study the synthesis and thermodynamic properties of the hydrogen absorption/desorption processes of nanostructured Mg-H, Mg-Ni-H, and Mg-Cu-H systems. Van’t Hoff equation of Mg-Ni-H system as well as formation enthalpy and entropy of Mg2NiH4was obtained by high pressure DSC method. The results agree with the ones by pressure-composition isotherm (PCT) methods in our previous work and the ones in literature.

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45

Bensalah, Jaouad, Amar Habsaoui, Brahim Abbou, Lamya Kadiri, Imane Lebkiri, Ahmed Lebkiri, and El Housseine Rifi. "Adsorption of the anionic dye methyl orange on used artificial zeolites: kinetic study and modeling of experimental data." Mediterranean Journal of Chemistry 9, no. 4 (November 18, 2019): 311–16. http://dx.doi.org/10.13171/mjc941911181112jb.

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The adsorption of methyl orange (MO) dye by artificial zeolites beads, used previously in the removal of heavy metal through the ionic exchange process, has been studied. The effect of several parameters such as temperature, MO concentration, and zeolite mass on MO adsorption was tested in order to determinate optimal conditions. All results have shown that the adsorption process was influenced by the studied parameters. The kinetic data concerning the study of temperature effect was modeled through pseudo-first-order and pseudo-second-order to determinate the adsorption mechanism. Thermodynamic parameters were calculated using the Van’t Hoff equation. Also, they have shown that the studied process has an endothermic, stable and spontaneous nature.

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46

Journal, Baghdad Science. "Kinetic and thermodynamic Studies Of Alanine Aminopeptidase(AAP) Isoenzymes I,II Partially Purified From Patient's Urine With Urinary Tract Cancer." Baghdad Science Journal 11, no. 1 (March 2, 2014): 70–80. http://dx.doi.org/10.21123/bsj.11.1.70-80.

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The activity of Alanine aminopeptidase( AAP ) was measured in the urine of healthy and urinary tract cancer patients , the results showed higher activity of (AAP) in patients compared to healthy . AAP was Purified from the urine of healthy and patients with urinary tract cancer by dialysis and gel filtration (Sephadex G – 50) and two isoenzymes of (AAP) were separated from urine by using ion-exchang resin (DEAE – Sephadex A – 50 ) in previous study. The kinetics studies showed that both isoenzymes I and II obeyed Michaelis – Menton equation . with optimal concentration of alanine-4-nitroanilide as substrate for isoenzymes I and II which was (2 x 10-3 mol/L ). The two isoenzymes obeyed Arrhenius equation up two 37° C and their Ea and Q10 constants were determined . The binding of alanine-4-nitroanilide by two isoenzymes I , II were studied and the kinetic constant ( k+1 , k-1 , Ka , Ks ) were indicated that the reaction was first order at 37° C .Thermodynamic parameters of the standard state ( ?G°, ?H° , ?S° ) and the transition state ( ?G*, ?H* , ?S* ) were determined by using Vant Hoff and Arrhenius equations.

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47

Bordbar, A.-Khalegh, Hamid Dezhampanah, Mozaffar Asadi, Elham Safaei, Nasrin Sohrabi, and Yadollah Khodadost. "Thermodynamics investigation of a series of metalloporphyrazine-bovine serum albumin complexes." Journal of Porphyrins and Phthalocyanines 11, no. 08 (August 2007): 556–65. http://dx.doi.org/10.1142/s1088424607000655.

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The equilibrium binding of the tetra-cationic complexes ( N , N ′, N ″, N ‴-tetra-methyltetra-2,3-pyridinoporphyrazinato)copper(II), ([ Cu (2,3- TMTPPA )]4+), ( N , N ′, N ″, N ‴-tetra-methyltetra-3,4-pyridinoporphyrazinato)copper(II), ([ Cu (3,4- TMTPPA )]4+), (( N , N ′, N ″, N ‴-tetra-methyltetra-3,4-pyridinoporphyrazinato)cobalt(II), ([ Co (3,4- TMTPPA )]4+) and (( N , N ′, N ″, N ‴-tetra-methyltetra-3,4-pyridinoporphyrazinato)zinc(II), ([ Zn (3,4- TMTPPA )]4+) with bovine serum albumin (BSA) has been studied in phosphate buffer pH = 7.0 and at various temperatures using multi-spectroscopy techniques. The results of resonance light scattering (RLS) studies represent no aggregate formation of porphyrazine in the surface of BSA and low tendency of these porphyrazine for aggregate formation. The binding constants and binding stoichiometries were determined by analyzing of optical absorption spectra of porphyrazine complexes at various concentration of BSA using SQUAD software. The results show that the best fitting corresponds to a 1:1 complex model between BSA and porphyrazines. The thermodynamic parameters were calculated by van't Hoff equation at various temperatures. The data indicate that the process is entropy driven suggesting that hydrophobic interactions play a considerable role in the complex formation. The binding of porphyrazine complexes to BSA quenches fluorescence emission of BSA via a dynamic mechanism and the quenching process obeys a linear Stern-Volmer relationship. The average aggregation number of BSA, which has been calculated from the analysis of fluorescence quenching data, indicates the absence of any porphyrazine induced aggregation of BSA due to its interaction with porphyrazine complexes. Fluorescence studies also indicate that porphyrazine is bound to site I of BSA placed in sub-domain IIA, where tryptophan 214 is located.

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48

Langenberg, Stefan, and Ulrich Schurath. "Gas chromatography using ice-coated fused silica columns: study of adsorption of sulfur dioxide on water ice." Atmospheric Chemistry and Physics 18, no. 10 (May 30, 2018): 7527–37. http://dx.doi.org/10.5194/acp-18-7527-2018.

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Abstract. The well established technique of gas chromatography is used to investigate interactions of sulfur dioxide with a crystalline ice film in a fused silica wide bore column. Peak shape analysis of SO2 chromatograms measured in the temperature range 205–265 K is applied to extract parameters describing a combination of three processes: (i) physisorption of SO2 at the surface, (ii) dissociative reaction with water and (iii) slow uptake into bulk ice. Process (ii) is described by a dissociative Langmuir isotherm. The pertinent monolayer saturation capacity is found to increase with temperature. The impact of process (iii) on SO2 peak retention time is found to be negligible under our experimental conditions.By analyzing binary chromatograms of hydrophobic n-hexane and hydrophilic acetone, the premelt surface layer is investigated in the temperature range 221–263 K, possibly giving rise to irregular adsorption. Both temperature dependencies fit simple van't Hoff equations as expected for process (i), implying that irregular adsorption of acetone is negligible in the investigated temperature range. Adsorption enthalpies of −45 ± 5 and −23±2 kJ mol−1 are obtained for acetone and n-hexane.The motivation of our study was to assess the vertical displacement of SO2 and acetone in the wake of aircraft by adsorption on ice particles and their subsequent sedimentation. Our results suggest that this transport mechanism is negligible.

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Norgren, Magnus, and Birger Lindström. "Dissociation of Phenolic Groups in Kraft Lignin at Elevated Temperatures." Holzforschung 54, no. 5 (September 6, 2000): 519–27. http://dx.doi.org/10.1515/hf.2000.088.

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Summary The dissociation of the phenolic groups in a polydisperse, low molecular weight kraft lignin (Indulin AT) was studied in alkaline aqueous solutions in the temperature interval 21–70 °C, using a UV-spectrophotometric method. It was found that at a constant concentration of hydroxide ions, the degree of dissociation was decreasing when the temperature was elevated. Dissociation curves and apparent pΚ 0 values were also calculated for the polydisperse sample at the same conditions, using the van't Hoff and the Poisson-Boltzmann equations. At degrees of dissociation exceeding α ≈ 0.4, the outcome of the theoretical approach showed to be in good agreement with the experimentally obtained results. Furthermore, calculations were performed for different molecular weights of kraft lignin and from this it was found that the apparent pΚ 0 is shifted to higher values by increasing molecular weight, due to an increased electrostatic attraction of the hydrogen ions, which is arising from a less curved surface. Predictions of the dissociation behavior at temperatures reached in the kraft process were performed and under these conditions, higher molecular weight lignin fragments seem never to reach the point of complete dissociation. It was also found that an increase in temperature results in phase separation in kraft lignin solutions with high ionic strengths and pH values close to the pΚ a of the phenolic groups.

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50

Largitte, L., and P. Lodewyckx. "Kinetics and Thermodynamics of the Adsorption of Lead (II) on a Activated Carbon from Coconut Shells." Eurasian Chemico-Technological Journal 15, no. 4 (October 15, 2013): 283. http://dx.doi.org/10.18321/ectj233.

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The effect of temperature on the adsorption of lead by an activated carbon from coconut shells is investigated. The pseudo second order equation is applied to the kinetic data obtained at different temperatures in order to determine the adsorption rate constants at these temperatures. Then, the Arrhenius equation is applied to the rate constants to determine the activation energy of the sorption reaction and the pre-exponential factor. By applying the Eyring equation to the rate constants, the standard thermodynamic activation parameters of the sorption reaction can also be calculated. In addition, the isotherms of lead adsorption on the activated carbon from coconut shells, at different temperatures, are determined and fitted by the Langmuir equation. The Van’t Hoff equation is applied to the Langmuir equilibrium constants in order to determine the standard enthalpy of the sorption reaction. The other standard thermodynamic parameters<br />(Gibbs standard enthalpy and standard entropy) are deduced. The isosteric standard sorption enthalpy is also determined by using both the classical approach and an adapted Clausius Clapeyron equation. The results are identical. The value obtained is higher, but more correct than that of Langmuir. On the basis of these<br />thermokinetic parameters, the activated carbon from Coconut shells can be considered as a very efficient carbon for the sorption of lead and its sorption efficiency (rate and quantity) increase with the temperature.

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Journal articles on the topic 'Equation de Van't Hoff'

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